// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_ANIMATION_LINEAR_ANIMATION_H_
#define UI_GFX_ANIMATION_LINEAR_ANIMATION_H_

#include "base/macros.h"
#include "base/time/time.h"
#include "ui/gfx/animation/animation.h"

namespace gfx {

class AnimationDelegate;

// Linear time bounded animation. As the animation progresses AnimateToState is
// invoked.
class GFX_EXPORT LinearAnimation : public Animation {
public:
    // Initializes everything except the duration.
    //
    // Caller must make sure to call SetDuration() if they use this
    // constructor; it is preferable to use the full one, but sometimes
    // duration can change between calls to Start() and we need to
    // expose this interface.
    LinearAnimation(int frame_rate, AnimationDelegate* delegate);

    // Initializes all fields.
    LinearAnimation(int duration, int frame_rate, AnimationDelegate* delegate);

    // Gets the value for the current state, according to the animation curve in
    // use. This class provides only for a linear relationship, however subclasses
    // can override this to provide others.
    double GetCurrentValue() const override;

    // Change the current state of the animation to |new_value|.
    void SetCurrentValue(double new_value);

    // Skip to the end of the current animation.
    void End();

    // Changes the length of the animation. This resets the current
    // state of the animation to the beginning.
    void SetDuration(int duration);

protected:
    // Called when the animation progresses. Subclasses override this to
    // efficiently update their state.
    virtual void AnimateToState(double state) { }

    // Invoked by the AnimationContainer when the animation is running to advance
    // the animation. Use |time_now| rather than Time::Now to avoid multiple
    // animations running at the same time diverging.
    void Step(base::TimeTicks time_now) override;

    // Overriden to initialize state.
    void AnimationStarted() override;

    // Overriden to advance to the end (if End was invoked).
    void AnimationStopped() override;

    // Overriden to return true if state is not 1.
    bool ShouldSendCanceledFromStop() override;

private:
    base::TimeDelta duration_;

    // Current state, on a scale from 0.0 to 1.0.
    double state_;

    // If true, we're in end. This is used to determine if the animation should
    // be advanced to the end from AnimationStopped.
    bool in_end_;

    DISALLOW_COPY_AND_ASSIGN(LinearAnimation);
};

} // namespace gfx

#endif // APP_LINEAR_ANIMATION_H_
